HP-65 more on the card reader

[albertofenini]

Last update on S/N 1511A

We scoped as suggested (thanks for the idea) all the Voltages, Vbsw, Vcc, Vgg, Vss in different points.
These were all clean.
Before replacing the capacitor on the motor, we decided to swap the only thing we hadn't swapped until now : The keyboard
And that was it.
We used the keyboard from S/N 1333A and combined with the 1511A assembly it was giving clean RA/RB and clean WA/WB.
A little adjustment of the eccentric cam and it was working perfectly, reading and recording.
In this moment it has the 2 x 22microF and 1x 15 microF capacitors new, we may as well leave them.

At this point we tested the viceversa : we installed the defective keyboard into the 1333A assembly
(logic board, card reader and battery plate) and as expected the problem we had before was now
affecting this unit.

We looked very carefully at the keyboard with a magnifying glass, we cleaned it and there are no visually noticeable defects.

   

We still have an additional keyboard, but it misses the anode and cathode drivers,
we should transplant the actual ones and we feel it's a bit too risky.

Now that we have isolated the problem, how can we check the integrity of the keyboard pcb ?

Thanks everyone for the support !!